Electricity Analogy: Voltage, Current, Resistance, Power

In 1747, Benjamin Franklin discovered the principle of electrical charge conservation - an electric charge can not be created or destroyed, only collected. In 1750, Benjamin Franklin published an experiment proposal to prove lightning is electricity. Franklin collected electricity in a group of Leyden jars that he described as "a battery".

The electron was discovered in 1897 (almost 150 years later).

An electrical current can be demonstrated with water flowing through a hose. When the faucet is on, water pressure from a water tower pushes water out of the hose. The water tower is analogous to a battery. Instead of being filled with electrons, the water tower is filled with water.

Water pours from a water hose onto a rock (circled).



The job of the water tower is to maintain steady water pressure to the houses in the town it serves. Water pressure is required to send water from the tower to each home. If the tower increases water pressure beyond normal levels, pipes break and faucets leak as the infrastructure is unable to contain the extra pressure. In this analogy, water pressure is equal to voltage.

Water pressure = voltage

Steady pressure is proven when different homes turn on a faucet and receive water at similar speeds. The speed the water comes out of an outlet (faucet or hose) is the current.

Current can be used to describe electrons flowing around an electrical circuit, water flowing from a water tower to a home, and H2O water molecules flowing in a river.



Speed of water (or electrons) = current: Ampere / amp

With a higher current, power increases. Water power can also be increased by using a resistor (holding a finger over the end of a hose). By increasing the resistance, the speed of the water increases. Power is increased. Increasing resistance on a circuit increases friction and results in increased heat.

Partially blocking the water = resistance: Ohm



Previously, the water poured on the rock (circled). With increased resistance, power is increased and the water shoots beyond the rock.

Resistance + Current = power

A rudimentary electrical circuit connects the positive terminal of a battery through a light to the negative terminal of a battery.



With the analogy of water pressure made, we can modify our understanding of the circuit.

The water tower uses water pressure to send water to the home.

The water tower battery uses water pressure voltage to send water electric current to power the home light.

P = Power (Watts)
I = Ampere (Current), Inductance
V = Volt

The formula for power is:
I(t) * V(t) = P(t)

If voltage is doubled and ampere is halved, the power (Watts) is the same.

Amps * Volts = Wattage (measure of work electricity does per second)





The bulb converts the electric power into light and heat.

The "I" stands for Inductance though it is used as the symbol for Current or Ampere.

V = I * R
I = V / R
R = V / I

P = V * I (Power equals Voltage times Current)

Common equations